1. Field of the Invention
The present invention relates to a process for the manufacture of sheets of glass having modified characteristics with respect to transmission and reflection of radiant energy.
The present invention also relates to the product obtained by the process.
The sheets of glass conventionally used in motorcars, aeroplanes, and generically in transportation, as well as in the building field, transmit and reflect an amount of heat and light energy different from that incident on the glass depending on the characteristics of the glass.
These characteristics may be modified by depositing on one or both the outer surfaces, one or more thin layers of appropriate materials, by means of operations known in the art as cathodic sputtering and chemical deposition in a vapour state.
The thin layers externally deposited on the glass show, however, a series of drawbacks. They can be scratched by solid bodies, can be abraded in unfavourable environmental conditions (dust, hail, polluting gases and the like), and their adherence to the substrate can be impaired by chemical incompatibility with the substrate itself or by scarce cleanness. Operating disfunctions in the deposition apparatus can produce, moreover, disuniformity of the layer.
A further disadvantage is that when the outer layers are subjected to a high temperature they show a tendency to detach or crack.
An object of the present invention is to provide a process for the manufacture of glass capable of transmitting and reflecting an amount of radiant energy different from that transmitted and reflected by the original glass.
A further object of the present invention is to provide a sheet of glass having modified energy characteristics and being able to overcome the above mentioned disadvantages.
2. Description of the Prior Art
A method of ion implantation to obtain a modification of a surface is well known.
By this method it is possible to obtain in the treated materials, mechanical, electrical, optical, chemical and physical characteristics different from the original characteristics, with the object of improving such characteristics or obtaining new alloys having certain properties.
A detailed description can be found in the text "Ion Implantation and Beam Technology" by J. S. Williams and J. M. Poate, issued by the Academic Press.
In the production technology of microelectronics, a high energy ion implantation method is presently used, in which the ions are capable of penetrating to a depth of several micrometers below the surface in contact with the external surface of the silicon substrate, on which the microcircuits are built.
By this method it is possible, by implantation of oxygen ions for instance, to obtain electrically insulated layers submerged into silicon and successively, by doping the silicon at a lower depth, to obtain conducting layers. In this manner microcircuits can be built inside the silicon substrate rather than outside. The microcircuits thus obtained are usually denominated "buried microcircuits".
A method of ion implantation for obtaining buried multilayer filters has been described in U.S. Pat. No. 4,262,056. This document teaches that an implantation of nitrogen into silicon at a temperature between 600.degree. and 1000.degree. C., produces layers of Si.sub.2 N.sub.4 at different levels, interleaved by pure silicon layers.
In this manner the creation of a new material is effected in the layer which has undergone implantation, which consequently shows a refractive index different from that of the original material.
This filter can, however, only be used in the infrared range, being in any case opaque to white light.